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I've recently had a retainer wall built in the landscape using the dry-stack method (see photos). Unfortunately, there has already been two occasions within past month of gopher activity behind the wall which has caused the soil to spill out onto the patio. I would like to seal the crevices between the stones with concrete to keep the gophers from pushing the soil outward. I'm not sure if portland cement or posthole concrete would be preferable. Although there isn't a french drain behind the wall, I don't think that drainage will be a problem as there should be plenty of smaller weep cracks for water to drain.

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  • That's unfortunate. It's a beautiful wall. Your best bet might be to excavate behind the wall in segments and install galvanized steel mesh against it (1/2" square hardware cloth, for example). – isherwood Nov 20 '19 at 19:22
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    Mesh might keep gophers out but not going to prevent gophers from pushing dirt through mesh and out through wall. Gophers are entering elsewhere, probably from neighbor's side of fence which is near wall in photos. – Grant Nov 20 '19 at 19:32
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    Then mesh over landscape fabric. You're in for a tedious and questionably effective task with the mortar. – isherwood Nov 20 '19 at 19:33
  • spray foam might be a lot easier and possibly more effective as it finds it's own path, just like the dirt. you might have to replace every 5 years or so, but who cares? hose out the cracks to remove any loose dirt, wait to dry, squirt in foam, trim, and enjoy. Embed broken glass into/behind the foam to discourage the varmints. – dandavis Nov 20 '19 at 19:59
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    Spray foam will look hideous. – Mike Baranczak Nov 20 '19 at 21:56
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I would expect that dry stacked stone would shift some, and that cement is too hard.

Consider using lime mortar instead. It's much slower drying, but isn't as brittle, and microcracks will self repair. Currently used a lot on strawbale construction.

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  • I'm not really concerned about the cement cracking a little. As you can see, it's an informal wall. Just interested in filling in the larger crevices so gophers can't push dirt out. – Grant Nov 20 '19 at 19:29
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Don't even try:

Dry stone walls are designed to shift slightly with the weather and with freeze/thaw cycles. They also drain freely, and, barring getting damaged by a falling tree or an earthquake, will last a hundred years with little or no maintenance.

There should be no soil between the stones, so either your contractor screwed up, or your gophers are particularly athletic.

Trying to pack inter-stone spaces with cement / foam / whatever is a losing proposition -- the cement will flex and crack and look pretty terrible within a few years, yet your gophers will be able to get through the smaller holes.

Instead, I'd recommend sweeping up any soil, applying fox urine, and encouraging local snakes to take up residence in your stone walls. Barring that, you could also invest in a bunch of gopher traps.

Alternatively, you could dig out behind the stone wall and backfill it with small rocks so the soil is not directly against the wall. This will prevent the gophers from pulling the soil through the wall. But this would involve digging up your garden.

So, I'd suggest just living with it.

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Consider one of the landscape or post-hole expanding foams. (example)

I've never used it, but it looks handy. Nice looking retaining wall!

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